Fully Analog DC Motor Speed Controller
A closed-loop DC motor speed controller built entirely from analog components, using magnetic encoder feedback.
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Overview
This project implements precise closed-loop speed regulation for a DC motor without any digital control — the entire feedback loop, from encoder signal conditioning to the drive stage, is analog.
A magnetic encoder provides real-time speed feedback, which is conditioned and compared against a reference signal using op-amp based error amplification. The resulting error signal drives the motor stage, forming a continuous analog feedback loop that regulates speed against load disturbances.
Designing this without a microcontroller forced a much deeper engagement with the underlying control theory — every gain and time constant in the loop had to be set through component selection rather than a tunable software parameter.
Key Features
- 01Closed-loop analog speed control using magnetic encoder feedback
- 02Op-amp based error amplification and reference comparison
- 03Fully discrete drive stage — no digital control loop
- 04Tuned for stable regulation under varying load on a 750 RPM N20 DC motor